Among the more common conditions shared by humans generally is the presence of lesions on the skin, many of which contain pigments in one or more colors and some of which are considered abnormal although not always dangerous to the individual. Typical examples of naturally occurring pigmentations include freckles; age or liver spots; birthmarks; malignant melanomas; nevi (melanocytic, epidermal, vascular, and connective tissue); and lentigines (brown spots on the skin or mucous membrane). In addition, a person's skin may have discoloring abnormalities due to vascular lesions which are caused by an abundance of enlarged blood vessels. Common examples of discolorful vascular lesions are "port wine" stain birth marks; telangiectasis, a colored spot formed most commonly on the skin by a dilated capillary or other small blood vessel; and hemangioma, a highly visible benign tumor composed of well-formed blood vessels and classified as capillary or cavernous.
In comparison, intervention created pigment containing lesions are commonly called "tattoos" and are commonly divided into two different categories: human-caused tattoos and traumatic-inflicted tattoos. Traumatic-inflicted tattoos are created typically as a result of accidents or other mishaps which cause scrapes, abrasions, explosion, or lacerations in a manner such that foreign material inadvertently becomes embedded into the skin. During the healing process, the skin becomes pigmented and often scarred as a result. In comparison, human-created tattoos are a popular form of skin decoration and self-expression in many cultures and societies. A common example here in the U.S. is the tattooed sailor; and it has been estimated that as many as 10% of the U.S. general population have tattoos somewhere on the skin of their bodies.
It will be recognized and appreciated that many persons at some point in their lives wish to remove pigment containing lesions, whether normal or abnormal, from their skin for health and/or cosmetic reasons. Even those individuals who voluntarily choose to create pigmented patterns on their skin may subsequently in their lives choose to undergo treatment designed to remove the pigmented lesion--often because of advancing age, or via a change in lifestyle, or as a consequence of a new personal relationship. Presently existing modes of removal treatment may achieve some clearing or lightening of pigment containing skin areas but only at substantial risk to the individual because of severe changes to the natural pigmentation and coloring of the skin or by incurring actual scarring of the treated skin area. The risks and severity of the multiple problems and consequences associated with removing pigmentations and other lesions generally of the skin is represented and illustrated by the difficulties of removing tattoos. However, it is explicitly understood that tattoos are merely one prototypic example of the different pigment containing lesions known which require removal.
As is the circumstance with many kinds of pigment containing lesions, the pigment lies inside the skin (i.e., the dermis or epidermis) and destructive modes of treatment have been employed conventionally to remove this pigment. Thus, a major problem of known treatments has been access to the epidermal or dermal pigment; and the only way it has been possible to remove the pigment(s) without using laser apparatus has been to remove all the skin around the pigmented lesion from the most exterior surface downwards into the deep tissues.
The conventional modes of treatment used for removal of pigmented lesions generally thus presently include: surgical excision and skin graft; dermabrasion; saliabrasion; cryosurgery; and laser light generated by CO.sub.2, argon, Nd:YAG, and ruby lasers [Hirshowitz, D. E., Plast. Reconstr. Surg. 373-378 (1980); Scutt, R. W. B., Br. J. Hosp. Med. J. 8:195 (1972); Manchester, G. H., Curtis 7:295 (1971); Clabaugh, F. M., Plast. Reconstr. Surg. 55:401 (1975); McDowell, F., Plast. Reconstr. Surg. 53:580 (1974); and Groot et al., J. Am. Acad. Dermatol. 15:518-522 (1986)]. While each of these modes of treatment has its own committed group of adherents, practitioners, and supporters, all of them unfortunately create as many problems as they cure concomitant with using the conventionally known procedures.
For example, a well recognized problem and drawback with some presently known laser treatment methods is that these routinely cause damage to both pigmented and non-pigment cells in the skin without discriminating between them. Laser treatment of pigment containing skin lesions has varied markedly from merely the superficial to extreme depth in the skin with little attempt to control the kind or the amount of tissue and cells destroyed. Moreover, some laser treatment processes known to date almost always cause a major change in skin texture; the skin is thus substantially altered from being smooth, elastic, and mobile to being hard and immobile and to becoming bumpy, cratered, or even pitted. In addition, conventional laser treatments cause a loss of the normal skin markings (normal ridges and valleys) as well as changes in normal skin pigmentation (losses as well as increases in normal skin color). Therefore, the resulting change in skin texture is almost always accompanied by a consequential change in skin color in which the skin at the treated site is no longer normal in pigmentation. Instead, the treated skin site appears either porcelain-white or mottled with dark pigment, both of these conditions resulting from either loss of all pigment or the implanting of pigment in the dermis instead of the epidermis. All of these radical and undesirable consequences and changes result from extensive, severe damage induced by the presently known laser treatment modalities and treatment methods.
Even the ruby laser (the best of the conventionally used laser systems) and the known procedures using the ruby laser have been demonstrated to be flawed, deficient, and inefficient for removing pigmentations, lesions, and abnormalities from the skin of a living human. As has well been described in the art, there are many problems and deficiencies concomitant with or caused by the ruby laser system and its various modes of use. In one mode, the ruby laser emits its laser light pulses called a normal pulse Another known way to operate and use the ruby laser is in the Q-switched mode; short bursts of pulses are emitted called a pulse train. A pulse train becomes problematic when the pulses are of low power. When this occurs, provided the pulses are discharged frequently enough and in spite of the short pulses being in the nanosecond range, the effect on the living tissue is similar to that of a continuous wave (CW) laser, which produces a highly indiscriminate effect. Moreover, instead of destroying the targeted structure with each pulse and, because the ruby energy output is low, there is only sufficient energy to partially alter the pigment containing lesion. Also, due to the characteristics of the ruby laser itself, the intensity of each pulse burst can meaningfully vary and it is very difficult for the practitioner to control the light energy dose delivered to each laser exposed site.
In addition, there presently is no convenient or easy way of precisely delivering the laser light beam to the patient. A common way of performing this manipulation at present is by the use of an articulating arm which is not only cumbersome but also easily goes out of alignment. This difficulty results in a further decrease of laser energy available to destroy the targeted tissue, thus making the ruby laser system even less efficient for removing abnormal pigmentations. Also, when used in the non-Q switched mode the ruby laser often produces severe scarring of the skin.
Another way to operate and use the ruby laser system conventionally is in the Q-switched mode. In this alternative mode of use, a single energy pulse of short duration (nanoseconds) is delivered to the skin by the ruby laser. However, despite the usage of Q-switched ruby lasers in clinical studies since the 1960's, the only currently available means of delivering treatment energy pulses in this manner is again by means of an articulated arm which is not only difficult to align and is bulky, but also creates "hot spots" within the delivered light beam area. One reported study revealed that multiple treatments using the ruby laser in the Q-switched mode removed at least 90% of the normal coloration in the skin. Adverse effects of hyper- and hypo-pigmentation were noted in some patients; and pigmented lesion sites composed of colors other than blue-black were not affected directly but instead showed a severe whitening of the skin as a result of this treatment [Read et al., Br. J. Plast. Surg. 36:455-459 (1983)]. Another study [Taylor et al., Arch. Dermatol. 126:893-899 ( 1990)] reported substantial lightening or total clearing of skin in 78% of amateur tattoos and 23% of 13 professional tattoos. However, this report demonstrated that multiple retreatments were required; transient hypopigmentation was seen in 50% of treated skin sites; and notable scarring appeared in approximately 6% of treated patients.
It is not surprising, therefore, that there is major interest in developing new and improved laser delivery systems which may be used in a carefully controlled method and treatment procedure for removing pigmentations from the skin of a living human. It will be recognized and appreciated also that while the development of new laser equipment and new laser delivery systems constitutes one discrete area of technical research, such efforts are meaningfully different and distinct from other investigations directed to developing a clinical process and methodology under carefully controlled operational parameters which would be effective and usable by a dermatologist or other medical practitioner. Equally important, the development of a clinically effective therapeutic treatment using a carefully controlled laser apparatus and laser delivery system which would prevent hypo-and/or hyperpigmentation as well as avoiding cratering/pitting and elevation or destruction of dermal and/or epidermal layers of the skin would be generally recognized as a major improvement and advance by practicing dermatologist and clinicians treating patients on a regular basis.